My brother just purchased a 1988 240 sedan, auto, 186k, for $900. The car does seem a bit sluggish in accelerating from a stop. (I had a 740 for many years which was no rocket, as a point of comparison.) On the bright side, there is no stalling. The idle seems low enough and it is decently smooth. There is mild engine vibration at idle, but it's minor enough that I am assuming he needs to drop $200 on replacing the rubber engine mounts.

The main worry is an air hissing sound coming from the pedal area when braking. This asthmatic air-leaking sound is consistent with every pedal press. The brakes do work without excessive effort, and begin to engage soon after downward pedal travel begins, but they feel spongy on they way down, similar to the feeling you get while bleeding brakes. The pedal ends up uncomfortably close to the floorboard, but the car stops adequately well with no pulling to either side.

My brother doesn't DYI, and while I have done my share of work on an old 122 and the 740, I'm far from expert. I'm new to 240's and have never changed a brake booster unit. It must be working at least somewhat, so I'm crossing my fingers that there might be a less painful solution. Maybe we have air in the hydraulic system, or some easier fix comes to mind?

Thanks,
Mike

 

You are on the right track. First look for a leak whence the air escapes, most likely the hose at the booster, it shouldn't be too hard to find. The boosters rarely go bad.

 

That does sound encouraging. I'm going to look for that booster hose and check for leaks. Could it explain the spongy pedal stopping near the floorboard?

 

Stopping near the floor sounds more like a leak in one of the brake circuits. Have you checked the level of the brake fluid? My guess is that you will see one of the reservoirs is low. If this is the case, then you have a leak in the brake lines somewhere.

On my '90, I just had my "octopus" go bad. This is the junction box just below the master cylinder that splits the lines that go to each brake caliper. Mine started leaking and I lost my braking on one of the circuits. Brakes still worked ok but the pedal was pretty low. The brake failure indicator did not light in my case - most likely because the sensor for the light is in the octopus.

 

Thanks for the idea. The brake fluid in the reservoir looks fine, both circuits are at the proper level, and the fluid does not look suspiciously fresh. In a test with with no hands on the steering wheel, there was no pulling during a hard stop. The car stops well enough that I believe all brakes are working.

 

Well the 240 has an extremely robust braking circuit. When you lose one circuit you still have braking on both front brakes and one rear so you really don't experience pulling etc. Once my '90 240 lost a circuit an my wife didn't notice except for the low pedal and the brake idiot light came on.

If there isn't fluid loss, no air in the lines and you have a low pedal, it could be a bad master cylinder. Main point is that a vacuum leak or problem with the booster should not give you a low pedal.

 

Thanks for filling in some useful details. I'm learning fast.

What could be causing that hissing sound? I guess it is a bad booster or booster hose or fitting. But the booster seems to be working...

 

Sounds can be hard to describe over the internet. My brake pedal makes a "squishing" sound when I press it and that is normal as far as I can tell. If your booster had a leak I would expect it would affect the engine idle. Do a google search for 'brake booster leak volvo 240' and most symptoms involve engine running/idling due to the vacuum loss and/or hard brake pedal and poor braking.